1. Field of the Invention
The present invention relates to a process for producing a thin film with MEMS probe circuits, and more particularly to a method of fabricating a flexible thin film integrated with various electrical circuits, plural probes and circuit contacts, a raised probe supported-spacer, and dielectric layers as a whole.
2. Description of the Prior Art
With the rapid development of the semiconductor technology, many consumed electronics products are getting smaller and smaller and provided with higher density of the integrated circuit as well as relevant electronic components, more pins, and shorter pin spacing. Moreover, due to the improvement on packaging technology, a contact is no longer arranged on the periphery of an integrated circuit but as an array. In the meantime, a contact pad, such as a tin ball or a gold bump, is used as material for contacts on a semiconductor surface, rather than a simple aluminum pad. Due to wireless communication times being coming, it means the electronic products are required for higher computation speed now. With a result, the difficulty is increased in implementation of high frequency tests and the development for the industry is then encountered some bottlenecks in capacity, cost, and future technology.
The structure of current wafer test card has been improved to solve the problems in test technology by increasing test speed, reducing test cost and reducing risk of misjudging good products. Therefore, the current wafer test card has developed from traditional cantilever probe cards to various vertical probe cards, rigid microelectro-mechanical systems (MEMS) probe cards and thin film test cards.
Difficulty in implementing an array test is improved substantially with the vertical probe card. However, the vertical probe card is expensive and difficult to make. Moreover, spacing above 100 μm is mainly used for the test of contact pads and it is difficult to create smaller spacing.
The kind of rigid MEMS probe used for rigid MEMS systems probe card is fabricated on a multi-layer ceramic substrate using semiconductor process technology. Difficulty in being arranged as an array and implementing high frequency tests has been removed by using the rigid MEMS probe card. However, since the rigid probe is inflexible and too much rigid, the contact pad of an item to be tested will be crushed easily if the contact pressure between the rigid probe and the contact pad is too high. Moreover, if a surface of the rigid probe or contact pad is uneven, the probe will not be easily in contact with the contact pad due to the inflexibility of the probe.
FIG. 1a shows the structure of a currently used thin film test card 20. A probe or metal bump 21 is fabricated on a contact which is placed on the surface of a flexible circuit thin film or a flexible circuit 28 of any kind.
Without a covered structure around the probe 21 to enhance strength, the probe 21 of the thin film test card 20 is attached to the surface of the flexible circuit 28 with the bottom of the probe 21 so that the structure of the probe 21 of the thin film test card 21 become is quite unstable at all. When exposed to pressure, as shown in FIG. 1b, the probe 21 will be easily crooked or sunken, which results in incorrect test results.
On the other hand, the probe 21 of the thin film test card 20 after being fabricated is usually installed in a protecting holder. However, since the circuit board 28 is so flexible and on the back surface opposite to the surface installed the probe 21 of the flexible circuit 28 is not provided with any supported blocks or fixing mechanism thereof, the probe 21 becomes crooked or uneven if the flexible circuit 28 is bent as shown in FIG. 1c, resulted in that the assembly of thin film test card 20 will be more difficult.
Since the probe 21 of the thin film card 20 has the above mentioned shortcomings in structure and is not easily arranged as an array, the availability of the thin film test card 20 for test purpose is limited and the test card 20 is only applicable to the test of products or panels with contact pads arranged around ICs.